Mainly capitalize the first letter.
(Followup to CL 54351.)

Change-Id: I2d5c3d72c53d3468de7a9d4af8bd009182ff3d38
Reviewed-on: https://go-review.googlesource.com/78114
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>